Titanium nanoholes meta-surface for ultra-broadband infrared absorption

Wideband absorbers are desirable for optoelectronics. Nevertheless, the absorption platforms are usually with broad spectral absorption but complex structure or narrowband absorption but simple design. Herein, a new infrared broadband absorption platform formed by a titanium nanoholes array is theoretically proposed and numerically demonstrated. The full absorption width at half-maximum is about 84% and the average absorption in the whole wavelength range from 0.75 μm to 3.25 μm is also up to 80%. Optical cavity with strong optical field coupling effect has been utilized to enhance the absorption in the wideband spectrum. Moreover, in sharp contrast to the narrowband absorption for the system with noble metal, ultra-broadband absorption is achieved in the platform due to the using of titanium metal. Furthermore, the absorption features including the bandwidth and operating wavelength positions can be both manipulated via the structural parameters. Strong plasmonic resonant coupling and photonic cavity trapping via the metal and dielectric resonators are the main contributions. These findings could be interesting for the broadband absorber platform, light flow modulator, etc. Keywords: Plasmonics, Broadband absorber, Optical cavity, Titanium